Nutrient absorption and utilization by wing and flight muscle morphs of the cricket Gryllus firmus: implications for the trade-off between flight capability and early reproduction

Journal of Experimental Biology

Behmer

2014

Although life-history trade-offs result from the differential acquisition and allocation of nutritional resources to competing physiological functions, many aspects of this topic remain poorly understood. Wingpolymorphic insects, which possess alternative morphs that trade off allocation to flight capability versus early reproduction, provide a good model system for exploring this topic. In this study, we used the wingpolymorphic cricket Gryllus firmus to test how expression of the flight capability versus reproduction trade-off was modified across a heterogeneous protein-carbohydrate nutritional landscape. Newly molted adult female long-and short-winged crickets were given one of 13 diets with different concentrations and ratios of protein and digestible carbohydrate; for each cricket, we measured consumption patterns, growth and allocation to reproduction (ovary mass) versus flight muscle maintenance (flight muscle mass and somatic lipid stores). Feeding responses in both morphs were influenced more by total macronutrient concentration than by protein-carbohydrate ratio, except at high-macronutrient concentration, where proteincarbohydrate balance was important. Mass gain tended to be greatest on protein-biased diets for both morphs, but was consistently lower across all diets for long-winged females. When long-winged females were fed high-carbohydrate foods, they accumulated greater somatic lipid stores; on high-protein foods, they accumulated greater somatic protein stores. Food protein-carbohydrate content also affected shortwinged females (selected for early reproductive onset), which showed dramatic increases in ovary size, including ovarian stores of lipid and protein, on protein-biased foods. This is the first study to show how the concentration and ratio of dietary protein and carbohydrate affects consumption and allocation to key physiological features associated with the reproduction-dispersal life-history trade-off.

Section: P<0001supporting

confidence: 89%

Nutritional physiology of life history trade-offs: how food protein-carbohydrate content influences life-history traits in the wing-polymorphic cricketGryllus firmus

Clark

Journal of Experimental Biology

Behmer

2014

“…On the standard diet, used in this study, LW(f) and SW lines differ to only a small degree (!10%) in total food consumption or assimilation of total nutrients, protein, lipid, or carbohydrate from ingested food (Zera and Brink 2000;A. J. Zera, unpublished data).…”

Section: Discussionmentioning

confidence: 93%

Intermediary Metabolism and Life‐History Trade‐Offs: Differential Metabolism of Amino Acids Underlies the Dispersal‐Reproduction Trade‐Off in a Wing‐Polymorphic Cricket

The American Naturalist

Zhao

2006

Although the differential flow of metabolites through alternate pathways of intermediary metabolism is thought to be an important functional cause of life-history trade-offs, this phenomenon remains understudied. Using a radiolabeled amino acid, we quantified genetic differences in in vivo amino acid metabolism between morphs of the wing-polymorphic cricket Gryllus firmus that trade off early-age reproduction and dispersal capability. Lines selected for the flight-capable morph, which delays reproduction, oxidized a greater proportion of radiolabeled glycine and converted a greater amount into somatic lipid, mainly triglyceride (flight fuel). By contrast, lines selected for the flightless, reproductive morph converted a substantially greater proportion of glycine into ovarian protein. Compensatory interactions between amino acid and lipid metabolism make up a key aspect of specialization for dispersal versus reproduction in G. firmus: increased oxidation of amino acids by the flight-capable morph spares fatty acid for enhanced conversion into triglyceride flight fuel. By contrast, increased oxidation of fatty acid by the flightless morph spares amino acids for enhanced biosynthesis of ovarian protein. Studies of amino acid and lipid metabolism in G. firmus currently represent the most detailed analyses of genetic modifications of intermediary metabolism that underlie a functionally important life-history trade-off found in natural populations. Trade-offs in internal resource allocation must result in large part from the differential flow of metabolites through pathways of intermediary metabolism. However, few data exist on the mechanisms involved. This is especially the case for genetically based life-history trade-offs, which are particularly relevant for understanding the mechanisms of life-history evolution. For example, only a few studies have documented in vitro differences in activities of enzymes of intermediary metabolism between lines that have been selected for different life histories (Harshman and Schmidt 1998;Harshman et al. 1999;Zera and Zhao 2003a). Only one study has reported variation in in vivo flux through a pathway of intermediary metabolism (de novo biosynthesis of triglyceride and phospholipid) that appears to contribute to a genetically based life-history trade-off (Zhao and Zera 2002). In short, the biochemical-metabolic mechanisms underlying life-history variation and evolution largely remain a black box. KeywordsAlterations in amino acid metabolism are expected to play an especially important role in the adaptive divergence of life histories. Amino acids can be metabolized by a variety of pathways (Clements 1959;Candy 1985;Stryer 1988), whose products can contribute significantly to somatic or reproductive functions (Boggs 1992). Amino acids are precursors of somatic (e.g., flight muscle) or re-890 The American Naturalist Figure 1: A, Metabolic fates of the amino acid glycine, investigated in this study: utilization for protein biosynthesis (pathway 1), oxidation to CO 2 via ...

“…Reduced nutrient availability can substantially magnify, while increased nutrient availability can diminish or obviate an apparent trade-off ( Figure 1) (Kaitala 1987, Chippindale et al 1993, Simmons & Bradley 1997, Nijhout & Emlen 1998, Zera et al 1998, Zera & Brink 2000; see clutch size studies in "Birds" section). These plastic responses of a trade-off are determined by priority rules, which govern relative allocation to organismal processes as a function of nutrient input.…”

Section: Trade-off Plasticity and Priority Rulesmentioning

confidence: 99%

The Physiology of Life History Trade-Offs in Animals

Harshman

2001

Annu. Rev. Ecol. Syst.

1,293

1,259

Abstract:The functional causes of life history trade-offs have been a topic of interest to evolutionary biologists for over six decades. Our review of life history trade-offs discusses conceptual issues associated with physiological aspects of trade-offs, and it describes recent advances on this topic. We focus on studies of four model systems: wing polymorphic insects, Drosophila, lizards, and birds. The most signifi cant recent advances have been: (a) incorporation of genetics in physiological studies of trade-offs, (b) integration of investigations of nutrient input with nutrient allocation, (c) development of more sophisticated models of resource acquisition and allocation, (d) a shift to more integrated, multidisciplinary studies of intraspecifi c trade-offs, and (e) the fi rst detailed investigations of the endocrine regulation of life history trade-offs.